37 research outputs found
Silver-Catalyzed Decarboxylative Alkynylation of α,α-Difluoroarylacetic Acids with Ethynylbenziodoxolone Reagents
A decarboxylating
alkynylation of α,α-difluoroarylacetic
acids with ethynylbenziodoxolone reagents is reported. AgNO<sub>3</sub> serves as the catalyst and K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> as the oxidant. A series of functional groups were tolerated, and
moderate to good yields were obtained
Efficient One-Pot Synthesis of Unsymmetrical Gold(I) N-Heterocyclic Carbene Complexes and Their Use as Catalysts
Eleven different goldÂ(I) complexes of new NHC ligands
were prepared
in excellent yield, demonstrating the versatility of the new route
to NHC complexes. While the influence of electronically different
ligands on the synthesis of the catalysts was small, the catalytic
activities of the products differed significantly
Saturated Abnormal NHCâGold(I) Complexes: Synthesis and Catalytic Activity
New
saturated abnormal N-heterocyclic carbene complexes of goldÂ(I) have
been prepared by a 1,3-dipolar cycloaddition of an in situ generated
azomethine ylide with an isocyanogoldÂ(I) choride. A series of different
substituents on the nitrogen atom of the 1,3-dipole are tolerated
without problem. Substitutents on a carbon atom of the 1,3-dipole
are problematic in the case of the isocyanogoldÂ(I) chlorides; only
low yields are obtained. However, the corresponding isocyanogoldÂ(I)
iodide shows good reactivity, and these abnormal N-heterocyclic carbenes
bear the substituent in a position α to the carbene carbon,
as proven by a crystal structure analysis of one of the products.
Some of the new saturated abnormal N-heterocyclic carbene complexes
were then tested in the gold-catalyzed phenol synthesis; moderate
turnover numbers of 252â380 could be reached
Efficient One-Pot Synthesis of Unsymmetrical Gold(I) N-Heterocyclic Carbene Complexes and Their Use as Catalysts
Eleven different goldÂ(I) complexes of new NHC ligands
were prepared
in excellent yield, demonstrating the versatility of the new route
to NHC complexes. While the influence of electronically different
ligands on the synthesis of the catalysts was small, the catalytic
activities of the products differed significantly
Gold Meets Rhodium: Tandem One-Pot Synthesis of ÎČâDisubstituted Ketones via MeyerâSchuster Rearrangement and Asymmetric 1,4-Addition
An asymmetric one-pot tandem Au/Rh-catalyzed synthesis of highly enantioenriched ÎČ-disubstituted ketones starting from racemic propargyl alcohols is disclosed. The compatibility of the two metal complexes (Au/Rh) and their orthogonal ligand systems (NHC/diene) in this bimetallic catalytic system is investigated
The Role of Gold Acetylides as a Selectivity Trigger and the Importance of <i>gem</i>-Diaurated Species in the Gold-Catalyzed Hydroarylating-Aromatization of Arene-Diynes
Terminal 1,2-dialkynylarenes undergo an unexpected cyclization
hydroarylation reaction toward naphthalene derivatives in benzene
as the solvent. The regioselectivity of the reaction can be controlled
by careful catalyst tuning. Also, the preparation of a bench-stable
cationic amine complex or simple heterogenization of the catalyst
on neutral aluminum oxide, which enables efficient catalyst recycling,
was possible. Intensive mechanistic investigations were undertaken,
giving new insights into the so-far underestimated role of acetylides
in gold chemistry. The gold plays a fascinating dual role serving
to both catalyze the reaction and activate the substrate by AuâC-Ï
bond formation. Evidence of <i>gem</i>-diaurated compounds
playing an important part for gold catalysis is also reported
The Role of Gold Acetylides as a Selectivity Trigger and the Importance of <i>gem</i>-Diaurated Species in the Gold-Catalyzed Hydroarylating-Aromatization of Arene-Diynes
Terminal 1,2-dialkynylarenes undergo an unexpected cyclization
hydroarylation reaction toward naphthalene derivatives in benzene
as the solvent. The regioselectivity of the reaction can be controlled
by careful catalyst tuning. Also, the preparation of a bench-stable
cationic amine complex or simple heterogenization of the catalyst
on neutral aluminum oxide, which enables efficient catalyst recycling,
was possible. Intensive mechanistic investigations were undertaken,
giving new insights into the so-far underestimated role of acetylides
in gold chemistry. The gold plays a fascinating dual role serving
to both catalyze the reaction and activate the substrate by AuâC-Ï
bond formation. Evidence of <i>gem</i>-diaurated compounds
playing an important part for gold catalysis is also reported
From Propargylic Amides to Functionalized Oxazoles: Domino Gold Catalysis/Oxidation by Dioxygen
A new, highly efficient, and atom-economic access to
a series of functionalized 2,5-disubstituted oxazoles from propargylic
amides is reported. A series of propargylic amides were transformed
to the corresponding alkylideneoxazolines by a goldÂ(I) catalyst. The
next step was an autoxidation to hydroperoxides bearing the heteroaromatic
oxazoles. Experiments addressing the reaction mechanism reveal a radical
pathway for this autoxidation process. The hydroperoxides could conveniently
be converted to the corresponding alcohols by reduction with sodium
borohydride
From Propargylic Amides to Functionalized Oxazoles: Domino Gold Catalysis/Oxidation by Dioxygen
A new, highly efficient, and atom-economic access to
a series of functionalized 2,5-disubstituted oxazoles from propargylic
amides is reported. A series of propargylic amides were transformed
to the corresponding alkylideneoxazolines by a goldÂ(I) catalyst. The
next step was an autoxidation to hydroperoxides bearing the heteroaromatic
oxazoles. Experiments addressing the reaction mechanism reveal a radical
pathway for this autoxidation process. The hydroperoxides could conveniently
be converted to the corresponding alcohols by reduction with sodium
borohydride
From Propargylic Amides to Functionalized Oxazoles: Domino Gold Catalysis/Oxidation by Dioxygen
A new, highly efficient, and atom-economic access to
a series of functionalized 2,5-disubstituted oxazoles from propargylic
amides is reported. A series of propargylic amides were transformed
to the corresponding alkylideneoxazolines by a goldÂ(I) catalyst. The
next step was an autoxidation to hydroperoxides bearing the heteroaromatic
oxazoles. Experiments addressing the reaction mechanism reveal a radical
pathway for this autoxidation process. The hydroperoxides could conveniently
be converted to the corresponding alcohols by reduction with sodium
borohydride